[Question #7482] Syphilis Testing Negative at 6 Weeks - Worried

3 months ago
Hi Dr's,

I am in a bad state of anxiety over a recent encounter and require your help please.

I received Oral sex from a woman (I am male) and about a week later, noted a 'tingling' in the end of my penis.

I have had STD anxiety before, multiple testing etc and do worry a lot about things.  To that end, three four days after the Oral Sex, I took Doxyclcline 100mg twice per day for 10 days, worrying about an STD such as Chlamydia.  (I had the these Antibiotics already as I was due to start a three month course for Eczema control)

I got myself googling and sure enough, started worrying about HSV1, and subsequently Syphilis.

I was checking my penis many times per day and discovered a very small ulcer, white in colour, around 4mm on the very extremity of the rolled back foreskin, this came on around 14ish days after the oral sex, due to the tingling, I thought it was possibly Herpes.

I plucked up the courage to get tested which I did at 45 days, I had a screen for HIV 1/2 p24 Antigen, Syphilis, Gonorrhea & Chlamydia, - all came back NEGATIVE the same day.

The small ulcer thing does not have an outer ring and is healing well, I have started to use Hydrocortisone once per day.  If anything, it looks like a self inflicted wound through retracting my foreskin too much, I appreciate goggle can be bad but it looks nothing like a Syphilis Chancre nor Herpes,  

With my exposure being Oral receiving only, and with a negative Antibody test at just over six weeks, can I close off the concern for Syphilis?  Or should I be re-testing?

There appears debate over the window period but I do note that most previous posts say six weeks, as do some of our NHS trusts now too.

Thank you.






H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
3 months ago
Welcome to the forum. Thanks for your confidence in our services.

Oral sex is low risk for all STDs -- not zero risk, but with much lower chance of infection than unprotected vaginal or anal sex. And your initial symptom (tingling alone) is not typical for any STD. Despite what you may have assumed or seen online, herpes never causes tingling as the only symptom. Your later penile ulcer could be herpes, which is overall the most common cause of genital ulceration. But if it's herpes, probably it is not a new infection from the exposure described. The timing isn't right for a new infection (symptoms usually within 3-5 days) and neither is such a mild, single lesion. If it's herpes, most likely you have been infected for months or years and have experienced a recurrent outbreak rather than a new infection. If the lesion persists, or if it recurs, see a doctor ASAP (within a day or two) so it can be swabbed and tested for HSV.

That said, there are plenty of other causes of minor genital ulcertation, especially under the foreskin in uncircumcised men. The doxycycline you took -- which was unnecessary and should not have been done, based on all you have said -- could have triggered a yeast infection. And your own observation that it has resulted from stretching your foreskin may also be possibility (although if you've had similar lesions before, it suggests herpes more than trauma).

As for syphilis, it's impossible:  doxycycline is 100% effective in aborting or treating syphilis. You could not develop a chancre 2 weeks after exposure, having been on doxy in the meantime. You do not need retestting for it.

Lay off the hydrocortisone. That's a good way to make eitiher herpes or a yeast infection worse, and also to delay healing of a traumatic lesion.

There is no debate among scientifically valid resources about the how long it takes various STD tests to become positive:  definitely 6 weeks for syphilis and for the AgAb ("fourth generation") HIV blood tests. 

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD
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3 months ago
Hi Dr Handsfield,

Firstly, I wish to say a huge Thank You to you.  You have certainly put my mind at rest, you sure have a great way with words if you don't mind me saying.

I wish to expand slightly further if I may, following the 'initial elation' of your reply, my mind starting 'wondering'.

When I received the Oral sex, I was a few weeks out of a five year relationship.  We were both tested fully as we entered that 5 year relationship, and have been faithful throughout.

During the time I was taking the Doxy (Started Day 4 for 10 days, 100mg, twice per day), I received a hand job from my partner of five years.  Once I had finished the 10 day course of Doxy, yet before the ulcer was found, we had unprotected intercourse. (This may mean the ulcer appeared around day 16, but not to split hairs, I would not have proceeded with any contact if I had known it was there, it could have also been there just I was not aware)

I assume the hand job was of no real risk, but could the unprotected intercourse (following completion of the 10 day course of Doxy) have put my ex girlfriend at risk?

My understanding is that a Penicillin shot (which I did not have) kills off Syphilis quickly and someone is then not infectious 24 hours later; does a similar rationale apply to the strength, length and dosage of Doxy that I took?

My thinking from your initial response is that whatever the ulcer thing is, it is not from Syphilis, and as such, I could not pass on, what I do not have?

Could the Antibiotics have perhaps not quite cured the Syphilis, yet simply delayed positive Antibodies?  (I remind myself of your '100% effective in aborting / curing')

I think I may be feeling an immense sense of guilt having received Oral sex and then potentially put my ex girlfriend at risk, this combined with the recent break-up is playing heavy on my mind.

If you can kindly advise on the above, I would be forever grateful Dr.

Best Wishes.

PS - I am trying to tell myself that the above scenario is irrelevant as you have already said that the ulcer cannot be from Syphilis.... I am trying to get my head clear :)

ie - the woman who gave me Oral would have had to have had it, I would have had to catch it, the Antibiotics not have aborted its onset and also created a delay to a positive AB test at 45 days)  - sounds almost implausible..... I hope....



H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
3 months ago
It is 100% certain you do not and could not possibly have syphilis. Your regular partner has no STD, so of course you could not have acquired any STD from her; and anyway, no STDs ever are transmitted by hand-genital contact.

"Could the Antibiotics have perhaps not quite cured the Syphilis, yet simply delayed positive Antibodies? " No, that isn't possible.

"I think I may be feeling an immense sense of guilt...." That's obviously the main problem here. Do your best to separate your guilt and shame from the potential medical consequences. They aren't the same. You have no STD from the oral sex event.
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3 months ago
Hi Dr,

Thank you for tour subsequent follow up.

I am pleased by what you have shared and I assume that it’s fair to say, if I had contracted Syphilis from this one time oral sex, the dosage of antibiotics and subsequent testing negative at six weeks concludes it would have gone.

My specific question in my response was really about the unprotected intercourse I had with my ‘ex / regular’ partner, just after I had taken the 10 days of Doxy. Would that course if treatment made that safe sex even if I had caught it from the oral sex some 15 days before?  

I appreciate I am  drilling down a little, Your words were so very reassuring last night, I just wish to feel I have not put my ex at risk and should not discussing testing with her.

The fact you said the Doxy would 100% kill the potential infection does reassure me, my concern has somewhat switched to worrying I have passed it on.  

Thank you for being patient with me, I almost have this put to bed now.

In summary, given everything I have shared,  can I feel assured that I have not passed Syphilis on to my ex, and that no further testing is required, for either of us?

Many Thanks Dr,


H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
3 months ago
Yes, doxycycline would have reliably cured any infection before you had sex with your partner. I've already said you cannot possibly have infected your partner. Suck it up, believe it, and move on.

That completes the two follow-up exchanges included with each question and so ends this thread. I hope the disucssion has been helpful. Best wishes and stay safe.
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